Vector-borne Viruses

Question 1

What are arboviruses

Answer 1

viruses that are transmitted by an insect

Question 2

How can insects acquire an arbovirus

Answer 2

through a blood meal of a reservoir or infected individual OR

vertical transmission between mother mosquito and offspring

Question 3

What are characteristics of arbovirus infections

Answer 3

viruses must establish a viremic (blood) infection

have access to virtually all organs increase the potential for severe disease

often have an insect and reservoir host and most of the time they do not cause disease in the insect or reservoir host

if the virus gets into a non-reservoir host it can cause severe disease

Question 4

The majority of viruses that use mosquitos as vectors belong to the ___ family(ies)

Answer 4

Flavivirus and Togavirus

one has the Bunyavirus

Question 5

What virus causes Yellow fever virus

Answer 5

Flavirus which is a simple + ssRNA virus

Question 6

What does the yellow fever virus cause

Answer 6

causes a hemorrhagic fever, symptoms include headache, backache, muscle aches, fever, and chills

Question 7

Where does yellow fever virus get its name

Answer 7

gets its name from the jaundice that is occasionally associated with the disease

Question 8

Where is yellow fever geographical distributed

Answer 8

virus is primary in South America and Africa

200,000 cases
30,000 deaths per year

Question 9

What mosquito spreads the yellow fever virus

Answer 9

Aedes aegypti mosquito

Question 10

Explain the yellow fever virus transmission cycle

Answer 10

main reservoir host is a monkey which is maintained in the sylvatic cycle (jungle cycle) and the viral infection does not cause disease in monkeys

occasionally a human will enter the jungle and become infected with the yellow fever virus

and this person can transmit the virus to another mosquito which can got into an urban area

an urban cycle can happen after this, this is when the virus spreads from the blood of a humans into the mosquito and then to other humans, may be a different mosquito than the sylvatic cycle mosquito

Question 11

What is the main reservoir of the yellow fever virus

Answer 11

monkey and is maintained in the sylvatic cycle

Question 12

What is the sylvatic cycle

Answer 12

the jungle cycle

mosquito to monkey and so on

Question 13

What was the first human virus discovered

Answer 13

yellow fever virus

Question 14

What is viremia

Answer 14

virus is in the blood and can easily spread to major organs

Question 15

What is the historical aspects of the yellow fever virus

Answer 15

brought to the Americas during the years of the slave trade, also brought the mosquitos

has played an important role in the human history especially in the wars in South America and the Caribbean

Napoleon in 1801 sent 40,000 troops to Haiti only 3000 returned most of the remaining ones died of yellow fever

Mexican-American war of 1846-47 10X more soldiers were killed by yellow fever than by battle

1901 Walter Reed confirmed the route of infection and nature of the agent of disease

Question 16

What are the detailed aspects of yellow fever disease

Answer 16

1. virus elicits an innate immune response that leads to production of pro-inflammatory cytokines at the site of infection
2. cytokines recruit immune cells to the site of infection, the virus gets into the immune cells
3. infected immune cells traffic to the lymph nodes
4. virus amplifies in the lymph nodes and enters the circulatory system (viremia)
5. they then travel to the liver, the liver is the primary target
6. large number of hepatocytes die from the virus infection or apoptosis
7. cytokine storm which causes damage to many cells throughout the body that leaves to hemorrhage (leaking of blood)

Question 17

How is yellow fever prevented or treated

Answer 17

vaccine that affords lifelong protection

yellow fever still afflicts several hundred thousand individuals each year

other methods to prevent mosquito bits have limited affects (bed nets)

Question 18

Is it possible to eliminate yellow fever

Answer 18

nearly impossible to eliminate due to the inset and vertebrate reservoirs

can limit infection by vaccines

Question 19

What virus causes the the Dengue Virus

Answer 19

Flavivirus which is +ssRNA

Question 20

Where geographically is the dengue virus

Answer 20

mainly in Asia and Latin America

endemic in southeast Asia, Africa, Caribbean and the Americas

Question 21

How many cases of dengue virus is there

Answer 21

estimate 400 million cases each year

500,000 get severe disease and 2.5% of cases result in fatality

40% of worlds population at risk

Question 22

How is dengue virus transmitted

Answer 22

between humans by Aedes aegypti and also Aedes albopictus

in 1960s it was only known to occur in a few countries since then it has spread to more than 100 countries

40% of worlds population is at risk

Question 23

What are aspects of the dengue virus cases

Answer 23

complex disease

95% of cases result in asymptomatic or mild disease

even in the mild cases the virus often caused headaches and muscle/ joint pains that eventually gave the virus the name break bone fever

in 5% of cases the dengue fever progresses to a more severe, life-threatening fever/ shock syndrome

Question 24

What are aspects of the dengue virus disease

Answer 24

complex disease

hemorrhagic fever associated with GI bleeding and plasma leakage

can lead to hepatic failure which generates the shock syndrome

virus illicits a very strong innate immune response called a cytokine storm

brings immune cells to the sites of vascular damage and thus causing further damage

Question 25

What is ADE

Answer 25

antibody dependent enchantment

Question 26

What virus causes antibody dependent enhancement

Answer 26

dengue virus

Question 27

How does dengue virus cause an antibody dependent enchancment

Answer 27

dengue virus exists as multiple serotypes, serotypes are groups of organisms with the same antigen

5 differs serotypes DENV-1, DENV-2 and so on

epitopes are slightly different between the different serotypes

antibodies can bind and neutralize DENV-1 , but if someone was infected with DENV-2 the antibody would bind to DENV-2 but would not neutralize t, this also the dengue virus to infer macrophages

the macrophages have bonded to the Fc region of the antibody and take up the virus, the virus wants to be inside of the macrophage to travel through the body, the virus can kill the macrophage after replication

rapid amplification of virus production occurs and this is called ADE

Question 28

Why is the dengue virus so hard to make a vaccine for

Answer 28

because it has 5 differs serotypes and this causes antibody dependent enhancement (ADE)

Question 29

What is the primary target of he dengue virus

Answer 29

macrophages

Question 30

What are possible treatment or prevention methods for he dengue virus

Answer 30

no vaccine

no therapeutics

only preventive measures are on reducing opportunities for the insects to persist in urban areas

supportive treatment (maintaining fluids and blood) can reduce mortality of severe cases from 10% down to 1%

Question 31

What virus causes the Chikungunya virus

Answer 31

alphavirus which is a +ssRNA

Question 32

Where was the Chikungunya virus first discovered

Answer 32

first discovered in 1952 in Tanzania (eastern edge of Africa)

Question 33

Where was the big outbreak of the Chikungunya virus and why did this likely occur

Answer 33

2005-2007 there was a large outbreak on reunion island (off the eastern coast of Madagascar)

1/3 of the population because infected

this resulted in rapid widespread distribution of southern Africa and Southeast Asia

this rapid spread was because of the change in mosquito vector, the mosquito that it enters into had a larger geographical range

Question 34

What are aspects of Chikungunya virus transmission

Answer 34

primary reservoir is not clear

several animal species including bats, birds, and primates can ac as reservoirs

originally transmitted by Aedes aegypit and its vector changed to Aedes albopictus since the outbreak on region island

the increase spread is because Aedes albopictus has an extend geographical range

Question 35

What are the disease symptoms of the chikungunya virus

Answer 35

disease is the result of extensive viremia

virus targets cells in he vicinity of the mosquito bite

virus is transmitted to secondary lymph glands

induces a cytokine storm

virus is carried into synovial tissue of joints by infected monocytes and macrophages where the inflammatory response is established

Question 36

What are the symptoms of the Chikungunya virus

Answer 36

symptoms occur in 4-30% of those infected

initial disease is self-limiting

it can include high fever, nausea, headache, rash, petechial spots and joint pain, low mortality rate of about .1%

joint pain is a major problem and it does not go away

joint pain appears in several episodes many months or years after initial infection

Question 37

How is CHIKV prevented or treated

Answer 37

no vaccine or therapeutic drugs

effort focused on controlling mosquito vector and addressing symptoms of the disease

anti-inflammatory drugs to reduce pains associated with severe arthritis caused by the virus

Question 38

Does CHIKV have a vaccine

Answer 38

no

Question 39

Does dengue have a vaccine

Answer 39

no

Question 40

Does Yellow fever have a vaccine

Answer 40

yes